Flow field plate and electrolytic bath

Abstract

The utility model relates to the technical field of flow field plates, in particular to a flow field plate and an electrolytic bath, at least one side of the flow field plate is provided with a flow field, and the flow field comprises a wave-shaped ridge which periodically extends in a cosine curve along a first direction; the multiple wave-shaped ridges are arranged at intervals in the second direction, the adjacent wave-shaped ridges are symmetrical in the first direction, and gaps between the adjacent wave-shaped ridges form flow channels which are continuously and alternately expanded and contracted; the eye-shaped ridge is arranged at the expansion part of the flow channel; the portions, on the two sides of the eye-shaped ridge, of the flow channel are high-pressure sides, the portion, on the contraction portion, of the flow channel is a low-pressure side, and raw materials on the high-pressure sides cross over the wave-shaped ridge to flow towards the low-pressure side. According to the application, the permeation of raw material water can be remarkably improved, the gas-liquid two-phase mass transfer is enhanced, and meanwhile, the performance in the aspects of flow uniformity and flow resistance is excellent.

Description

Technical Field

[0001] The invention relates to the technical field of flow field plates, in particular to a flow field plate and an electrolytic cell. Background Art

[0002] As a key water electrolysis technology, PEM (proton exchange membrane) electrolyzer is widely used in green hydrogen production due to its low operating temperature, rapid response and high hydrogen production efficiency.

[0003] The bipolar plate is one of the main components of the PEM electrolyzer. In addition to its role in electronic conduction and mechanical support, the more important thing is the impact of the flow channel design of the anode on the mass transport of the gas-liquid two-phase flow in the porous transport layer, the uniformity of the current density distribution, and the hydration of the membrane electrode, which in turn affects the performance and service life of the electrolyzer. Especially for large electrolyzers, the impact of the bipolar plate performance will be more significant. A good anode plate design helps to achieve higher electrolysis efficiency and current density, which is crucial to the large-scale production and supply of green hydrogen.

[0004] The anode design of the bipolar plate of the PEM electrolyzer is mainly designed around factors such as flow uniformity, raw water permeability, and flow resistance. The flow uniformity of the raw water reflects the permeation uniformity of the raw water in the porous transport layer and the catalyst layer, and the permeation uniformity directly affects the uniformity of the current density. As the generated oxygen continues to gather at the outlet, the volume fraction of oxygen inevitably increases gradually with the flow direction, thereby affecting the overall flow uniformity. Regarding permeability, the better the permeability of the raw water, the smaller the diffusion overpotential, which helps to achieve high current density operation of the electrolyzer to improve hydrogen production efficiency. Regarding flow resistance, generally, the greater the flow resistance of the bipolar plate, the better the permeability of the raw water in the porous transport layer and the catalyst layer, but the flow resistance increases the system power consumption and reduces the system energy efficiency, so there is a balance between flow resistance and permeability. Above, the main considerations and difficulties in the design of the bipolar plate anode of the PEM electrolyzer are summarized. Large electrolyzers have a large reaction area and require an efficient anode flow field structure to improve the overall performance of the electrolyzer. Summary of the invention

[0005] The purpose of the present application is to provide a flow field plate and an electrolyzer for large and ultra-large PEM water electrolyzers, wherein the flow field plate can significantly improve the permeability of raw water, strengthen gas-liquid two-phase mass transfer, and at the same time excel in flow uniformity and flow resistance.

[0006] The present application provides a flow field plate, at least one side of which is provided with a flow field, wherein the flow field comprises:

[0007] The corrugated ridges extend periodically in a cosine curve along a first direction; a plurality of the corrugated ridges are arranged at intervals along a second direction, adjacent corrugated ridges are symmetrical along the first direction, and the gaps between adjacent corrugated ridges form a flow channel that alternately expands and contracts;

[0008] an eye-shaped ridge, provided at the expansion of the flow channel;

[0009] The flow channels on both sides of the eye-shaped ridge are high-pressure sides, and the flow channels at the contraction are low-pressure sides. The raw materials on the high-pressure side flow over the wave-shaped ridge to the low-pressure side.

[0010] In the embodiments provided by the present application, the flow field is formed by wavy ridges and eye-shaped ridges. The wavy ridges and eye-shaped ridges are based on cosine curves as basic construction elements, combined with mirroring, arrays, and offsets to form a mesh-like flow field structure with three-dimensional flow characteristics to enhance the penetration of raw water into the porous transport layer.

[0011] The three-dimensional flow characteristics of the flow field structure are due to the alternating changes in the expansion and contraction of the flow channel, which forms alternating high-pressure and low-pressure sides on both sides of the corrugated ridge. The raw water on the high-pressure side will penetrate downward over the corrugated ridge and enter the low-pressure side of the flow field plate again through the porous transmission layer matched with the flow field plate, thereby enhancing the three-dimensional flow characteristics. This dense high and low pressure distribution greatly improves the mass transfer of the gas-liquid two-phase and strengthens the permeability and permeability uniformity of the raw water.

[0012] As a preferred embodiment of the present invention, the ratio of the ridge width s of the corrugated ridge to the width w of the flow channel is R, wherein 0.9≤R≤1.2.

[0013] In the above technical solution, R is controlled at 0.9 to 1.2. The larger R is, the larger the contact area is and the smaller the contact resistance is, but the flow area is reduced and the pressure drop is increased.

[0014] As a preferred embodiment of the present invention, the waveform amplitude of the waveform ridge is A, and the value of A is s / 2+w / 2.

[0015] As a preferred embodiment of the present invention, the number of waveform periods of the waveform ridge is m, where m is an integer.

[0016] In the above technical solution, the number of wave periods m is an integer to meet the symmetry requirements. The larger m is, the better the permeability and permeability uniformity will be. However, after reaching a certain value, the effect will no longer be significant, and too large m will increase the difficulty of design and manufacturing. Generally, the wavelength can be controlled between 13mm and 17mm.

[0017] As a preferred embodiment of the present invention, the number of the flow channels is 4n+1, wherein n is a positive integer.

[0018] In the above technical solution, the number of flow channels is 4n+1 to meet the symmetry requirement of the flow field.

[0019] As a preferred embodiment of the present invention, the flow field plate further comprises a first inlet and outlet flow channel connected to one end of the flow field, and the first inlet and outlet flow channel corresponds one-to-one with the flow channel.

[0020] As a preferred embodiment of the present invention, the flow field plate further comprises a second inlet and outlet flow channel connected to the other end of the flow field, and the second inlet and outlet flow channel corresponds one-to-one with the flow channel.

[0021] In the above technical solution, the first inlet and outlet flow channel, the second inlet and outlet flow channel and the flow channel of the flow field are connected, and the connected flow channels are independent of each other and do not interweave with each other. This greatly reduces the local blockage of the gas-liquid two-phase flow caused by flow turbulence, improves flow stability and reduces flow resistance.

[0022] As a preferred embodiment of the present invention, the first direction is perpendicular to the second direction.

[0023] In the above technical solution, the first direction is perpendicular to the second direction, which can better achieve the symmetry of the flow field.

[0024] An embodiment of the present application also provides an electrolytic cell, comprising the flow field plate described in any one of the above items.

[0025] Compared with the prior art, this application has the following beneficial effects:

[0026] 1. Compared with the general wavy flow channel, the present application has significant three-dimensional flow characteristics, greatly improves the permeability and permeability uniformity of raw water, can achieve higher current density, and improve the energy efficiency of hydrogen production by electrolysis;

[0027] 2. Compared with the traditional titanium mesh, the flow field plate of the present application has a lower contact resistance, enhanced structural strength, and better performance in flow resistance and heat conduction, and can achieve more stable performance and longer service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a partial schematic diagram of the corrugated ridges and flow channels of the flow field plate in an embodiment of the present invention.

[0029] Figure 2 It is a partial schematic diagram of the wavy ridge, eye-shaped ridge and flow channel in an embodiment of the present invention.

[0030] Figure 3 It is a partial schematic diagram of the flow channel in the reaction zone in an embodiment of the present invention.

[0031] Figure 4 It is a schematic diagram of a partial cross-section of the flow channel in the reaction zone in an embodiment of the present invention.

[0032] Figure 5 It is a partial schematic diagram of the reaction zone flow channel and the first inlet and outlet flow channel in an embodiment of the present invention.

[0033] Figure 6 It is a front schematic diagram of the flow field plate in an embodiment of the present invention.

[0034] Figure 7 Schematic diagram of the simulation of high and low pressure distribution of the flow field in an embodiment of the present invention.

[0035] Figure 8 It is a simulation schematic diagram of the permeability comparison between the embodiment of the present invention and the wave-shaped flow channel.

[0036] Explanation of the reference numerals: 1. wavy ridge; 2. eye-shaped ridge; 3. flow channel; 31. expansion portion; 32. contraction portion; 33. high-pressure side; 34. low-pressure side; 4. first inlet and outlet flow channel; 5. second inlet and outlet flow channel; 6. first inlet and outlet; 7. second inlet and outlet. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In the description of this application, it should be noted that the terms "wavy ridge", "eye-shaped ridge", "structural ridge" and "structural flow channel" are not professional terms, but descriptive terms defined according to the needs of achieving functions or construction.

[0039] The existing flow field plate design is mainly based on factors such as flow uniformity, raw water permeability, flow resistance, etc., to achieve a balance between permeability and flow resistance. Large electrolyzers have a large reaction area and require a more efficient anode flow field structure to improve the overall performance of the electrolyzer.

[0040] The applicant has designed the present application based on the above-mentioned defects of the prior art. The flow field plate and the electrolytic cell of the present application will be specifically described below in conjunction with specific implementation methods.

[0041] The flow field of the flow field plate is composed of wave-shaped ridges and eye-shaped ridges, and the gaps between the wave-shaped ridges and the eye-shaped ridges form flow channels for the raw material water to flow.

[0042] In order to improve the three-dimensional flow characteristics of the flow field structure, this application designs wave-shaped ridges and eye-shaped ridges with cosine curves as basic building elements, and forms a mesh-like flow field structure through mirroring, aligning, offsetting, etc., so as to enhance the penetration of raw water into the porous transmission layer.

[0043] Reference Figures 1 to 7 As shown, at least one side of the flow field plate is provided with a flow field, and the flow field comprises:

[0044] The corrugated ridges 1 extend periodically in a cosine curve along a first direction A; a plurality of the corrugated ridges 1 are arranged at intervals along a second direction B, and adjacent corrugated ridges 1 are symmetrical along the first direction A, and the gaps between adjacent corrugated ridges 1 form a flow channel 3 that alternately expands and contracts;

[0045] an eye-shaped ridge 2, provided at the expansion of the flow channel 3;

[0046] The flow channels 3 on both sides of the eye-shaped ridge 2 are high-pressure sides 33 , and the flow channels 3 at the contraction are low-pressure sides 34 . The raw water on the high-pressure side 33 flows over the corrugated ridge 1 to the low-pressure side 34 .

[0047] The flow field plate is also called a bipolar plate. The flow field is composed of a wave-shaped ridge 1 and an eye-shaped ridge 2 protruding relative to the flow field plate, and the gap between the wave-shaped ridge 1 and the eye-shaped ridge 2 forms a flow channel 3.

[0048] refer to Figure 1 As shown, the corrugated ridge 1 is constructed based on a cosine curve, a single corrugated ridge 1 extends along the first direction A, and a plurality of corrugated ridges 1 are arranged at intervals along the second direction B, and the spacing between adjacent corrugated ridges 1 is the same.

[0049] The adjacent wave-shaped ridges 1 are mirror-symmetrical with the first direction A as the axis, forming a continuously expanding and contracting flow channel 3, and the cross-sectional area of ​​the flow channel 3 is continuously changing. Since the wave-shaped ridges 1 are smooth cosine curves, the cross-sectional area of ​​the flow channel 3 changes uniformly. The relatively expanded part of the flow channel 3 is the expansion part 31, and the relatively contracted part is the contraction part 32.

[0050] refer to Figure 2 As shown, the eye-shaped ridge 2 is arranged at the expansion portion 31 of the channel, and the eye-shaped ridge 2 divides the flow channel 3 into two branch flow channels, and the two branch flow channels merge into one flow channel 3 again after passing through the eye-shaped ridge 2.

[0051] Reference Figure 3 As shown, the raw water flows from the high pressure side 33 over the corrugated ridge 1 to the low pressure side 34. Figure 4From the perspective of the cross section, the raw water flows from the high-pressure side 33 to the low-pressure side 34 across the corrugated ridge 1. The three-dimensional flow characteristics of the flow field structure are due to the alternating changes in the flow cross section, so that the high-pressure side 33 and the low-pressure side 34 are formed on both sides of the corrugated ridge 1. The raw water on the high-pressure side 33 will penetrate into the porous transmission layer and enter the low-pressure side 34 through the porous transmission layer, thereby enhancing the three-dimensional flow characteristics.

[0052] This dense distribution of high and low pressure (see Appendix Figure 7 ) greatly improves the mass transfer of gas and liquid phases and enhances the permeability and permeability uniformity of raw water. Figure 8 As shown, compared with the existing ordinary wavy flow channel b, the design a of the present application has a higher raw water permeability in the porous transmission layer under the same working conditions.

[0053] In some possible embodiments, refer to the attached Figures 2-3 As shown, the eye-shaped ridge 2 is constructed based on the wavy ridge 1, and the shape of the eye-shaped ridge 2 cooperates with the wavy ridge 1 to form a flow channel 3 with a uniform width at all locations.

[0054] In some possible embodiments, refer to the attached Figures 1-2 As shown, the ratio of the ridge width s of the corrugated ridge to the width w of the flow channel 3 is R, where 0.9≤R≤1.2. The waveform amplitude of the corrugated ridge 1 is A, and A is s / 2+w / 2. The number of waveform periods of the corrugated ridge 1 is m, and m is an integer. The number of flow channels 3 is 4n+1, where n is a positive integer.

[0055] As the best embodiment, if the width of the reaction zone is 17 cm and the length is 30 cm, based on the reaction zone width of 17 cm, the number of structural channels 3 is taken as 77 (4*19+1), and the ratio of the structural ridge width to the structural channel 3 width is R=1.0, and the structural ridge width s=1.11 mm and the structural channel 3 width w=1.11 mm are calculated and the structural lines are divided accordingly; based on the reaction zone length of 30 cm, the number of waveform periods m=22 is taken, and the wavelength is calculated to be 13.64 mm, combined with the waveform amplitude A=(s+w) / 2=1.11 mm, a single waveform ridge 1 is constructed; the single waveform ridge 1 is mirrored with a margin of w / 2 to form an array unit; the array unit is arrayed 19 times with a unit spacing of 4*(s+w) to construct the entire waveform ridge 1.

[0056] Reference Figure 2 As shown, when constructing the eye-shaped ridge 2, based on the wave-shaped ridge 1, the wave-shaped curve is offset downward and upward (the offset distance is w) to construct the eye-shaped ridge 27 and form the eye-shaped ridge 2 array unit; similarly, the eye-shaped ridge 2 array unit is arrayed with a unit spacing of 4*(s+w) to construct the entire eye-shaped ridge 2.

[0057] In the reaction zone flow channel 3 formed by the corrugated ridge 1 and the eye-shaped ridge 2, the flow velocity decreases and the pressure increases due to the increase of the flow cross section on both sides of the eye-shaped ridge 2, so a high-pressure side 33 and a low-pressure side 34 are generated on both sides of the corrugated ridge 1. The resulting pressure gradient causes the fluid to flow from the high-pressure side 33 to the low-pressure side 34, but due to the presence of the corrugated ridge 1, the fluid on the high-pressure side 33 moves downward through the porous transmission layer into the low-pressure side 34, thereby enhancing the three-dimensional flow characteristics. The array distribution of this structure will greatly improve the overall permeability of the raw water, reduce the diffusion overpotential, and help achieve a higher electrolysis rate; at the same time, the higher the distribution density, the better the flow and permeation uniformity, which in turn helps to improve the uniformity of the current density, thereby improving the electrolysis efficiency.

[0058] In some possible embodiments, refer to the attached Figures 5-6 As shown, the flow field plate further includes a first inlet and outlet flow channel 43 connected to one end of the flow field, and the first inlet and outlet flow channel 43 corresponds to the flow channel 3. The flow field plate further includes a second inlet and outlet flow channel 53 connected to the other end of the flow field, and the second inlet and outlet flow channel 53 corresponds to the flow channel 3.

[0059] The first inlet and outlet flow channel 43 and the second inlet and outlet flow channel 53 are connected with the flow channel 3 in the reaction zone. The flow channels 3 that continuously intersect and separate between two adjacent corrugated ridges 1 form a through flow channel 3. The through flow channels 3 are independent of each other, making the flow smoother, greatly reducing the local blockage of the gas-liquid two-phase flow caused by flow turbulence, improving the flow stability and reducing the flow resistance.

[0060] In some possible embodiments, refer to the attached Figure 6 As shown, the flow field plate further includes a first inlet and outlet 6 and a second inlet and outlet 7, and the first inlet and outlet 6 and the second inlet and outlet 7 are both designed to be long strips to meet the needs of parallel access of multiple water inlet and outlet pipes. Large electrolytic cells require a large water flow rate, and the parallel access of multiple water inlet and outlet pipes can greatly reduce flow resistance while maximizing flow uniformity.

[0061] In some possible embodiments, due to the symmetry of the entire flow field structure, the first inlet and outlet 6 and the second inlet and outlet 7 can be used interchangeably, that is, they can be used as both inlets and outlets. As the volume fraction of oxygen increases toward the outlet, the working environment of the reaction zone inevitably becomes different. For large electrolyzers with a large reaction area, long-term operation may lead to differences in the distribution of membrane electrode performance. Therefore, regular replacement of the inlet and outlet can balance the impact of this difference, which can improve the stability of the electrolyzer performance to a certain extent and extend the service life of the electrolyzer.

[0062] In some possible embodiments, an electrolytic cell includes the flow field plate described in any one of the above items.

[0063] The implementation principle of this application is: a special flow field structure is used to construct a dense local high and low pressure distribution, thereby presenting a special pressure field distribution (pressure fluctuates and decreases along the flow direction), which greatly enhances the three-dimensional flow characteristics of the fluid and improves the permeability and permeability uniformity of the raw water. In addition, the independent through-flow channels greatly reduce the local blockage of the gas-liquid two-phase flow caused by flow turbulence, improve the flow stability and reduce the flow resistance. At the same time, the long strip inlet and outlet facilitate the side-by-side access of multiple inlet and outlet pipes, thereby further reducing the flow resistance and maximizing the flow uniformity. Finally, the symmetrical design allows the inlet and outlet to be interchanged, which is of certain significance to improving the stability of the electrolytic cell performance and extending the service life of the electrolytic cell. In general, the structural design reduces the diffusion overpotential and improves the uniformity of the current density by improving the permeability and permeability uniformity of the raw water, while achieving lower pressure loss through regular flow channel division and reasonable inlet and outlet design, thereby helping the electrolytic cell to achieve high electrolysis energy efficiency at high gas production rate.

[0064] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A flow field plate, characterized in that: At least one side thereof is provided with a flow field, and the flow field comprises: The corrugated ridges extend periodically in a cosine curve along a first direction; a plurality of the corrugated ridges are arranged at intervals along a second direction, adjacent corrugated ridges are symmetrical along the first direction, and the gaps between adjacent corrugated ridges form a flow channel that alternately expands and contracts; an eye-shaped ridge, provided at the expansion of the flow channel; The flow channels on both sides of the eye-shaped ridge are high-pressure sides, and the flow channels at the contraction are low-pressure sides. The raw materials on the high-pressure side flow over the wave-shaped ridge to the low-pressure side.

2. A flow field plate according to claim 1, characterized in that: The ratio of the ridge width s of the corrugated ridge to the width w of the flow channel is R, wherein 0.9≤R≤1.

2.

3. A flow field plate as claimed in claim 2, characterized in that: The waveform amplitude of the waveform ridge is A, and the value of A is s / 2+w / 2.

4. A flow field plate according to claim 1, characterized in that: The number of waveform periods of the waveform ridge is m, where m is an integer.

5. A flow field plate according to claim 1, characterized in that: The number of the flow channels is 4n+1, wherein n is a positive integer.

6. A flow field plate according to claim 1, characterized in that: The flow field plate further includes a first inlet and outlet flow channel connected to one end of the flow field, and the first inlet and outlet flow channel corresponds to the flow channel one by one.

7. A flow field plate according to claim 1, characterized in that: The flow field plate further includes a second inlet and outlet flow channel connected to the other end of the flow field, and the second inlet and outlet flow channel corresponds one-to-one with the flow channel.

8. A flow field plate according to claim 1, characterized in that: The first direction is perpendicular to the second direction.

9. An electrolytic cell, characterized in that: A flow field plate comprising the flow field plate according to any one of claims 1 to 8.

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